1. Technical Field of the Invention
The present invention relates to photoprotective compositions comprising amine, amide, sulphonamide and carbamate substituted benzalmalonic salts as sunscreens which are active in the UV radiation region.
The present invention also relates to novel amine, amide, sulphonamide and carbamate derivatives of benzalmalonic salts and to the various applications thereof.
2. Description of Background and/or Related and/or Prior Art
It is known that radiation with wavelengths between 280 nm and 400 nm allows browning of the human epidermis and that radiation with wavelengths between 280 nm and 320 nm, known as UV-B radiation, gives rise to erythema and skin burns which may be detrimental to the development of a natural tan. For these reasons and also for aesthetic reasons there is increasing demand for means of controlling this natural tanning. It is therefore advisable to screen this UV-B radiation.
It is also known that UV-A rays with wavelengths between 320 nm and 400 nm, which cause browning of the skin, are capable of inducing its impairment, particularly in the case of skin which is sensitive and/or continually exposed to sunlight. UV-A rays give rise in particular to a loss of elasticity in the skin and to the appearance of wrinkles, leading to premature skin aging. They promote the triggering of the erythemal reaction or amplify this reaction in certain individuals, and may even be the origin of phototoxic or photoallergic reactions. Consequently, for aesthetic and cosmetic reasons, such as the preservation of the natural elasticity of the skin, increasing numbers of individuals wish to control the effect of UV-A rays on their skin.
Organic sunscreens are usually formulated in compositions which are in the form of oil-in-water or water-in-oil emulsions. Organic sunscreens, which are generally lipophilic or hydrophilic, are present in solution in one or the other of these phases in amounts appropriate to provide the desired sun protection factor (SPF).
The sun protection factor is the ratio of the irradiation time required for the erythema-forming threshold to be reached in the presence of the screen under test to the irradiation time required for this same threshold to be reached in the absence of the screen.
In addition to their capacity to screen sunlight, the photoprotective compounds must also have good cosmetic properties, effective solubility in customary solvents, and especially in aqueous media, and satisfactory photostability.